BT Tower

Initially, the first 16 floors were for technical equipment and power. Above that was a 35-metre section for the microwave aerials, and above that were six floors of suites, kitchens, technical equipment and finally a cantilevered steel lattice tower. To prevent heat build-up the glass cladding was of a special tint. The construction cost was £2.5 million.
As well as the communications equipment and office space there were viewing galleries, a souvenir shop and a rotating restaurant on the 34th floor, called The Top of the Tower and operated by Butlins. It made one revolution every 22 minutes.
A bomb, responsibility for which was at first blamed on the Provisional IRA, exploded in the roof of the men's toilets at the Top of the Tower restaurant on 31 October 1971. In fact, the bomb had been placed there by members of the Angry Brigade, an anarchist collective. The restaurant was closed to the public for security reasons in 1980, the year in which Butlins' lease eventually expired. Public access to the building ceased in 1981. The tower is sometimes used for corporate events.
Due to its importance to the national communications network, the location of the tower was designated an official secret.
en.wikipedia.org/wiki/BT_Tower

1971: Bomb explodes in Post Office tower

news.bbc.co.uk/onthisday/hi/dates/stories/october/31/newsid_2464000/2464143.stm

The BT Tower (previously known as the London Telecom Tower) is a telecommunications tower, which also used to host viewing galleries and a rotating restaurant. (visitlondon.com/things-to-do/place/2233934-bt-tower) Nowadays closed to the public.

Look at Life - Eating high, 1966